This invention generally relates to the art of electrical connectors and, particularly, to an electrical connector assembly incorporating a spring-loaded terminal.
Numerous electrical connectors have been designed for utilization with a flat circuit which may be mounted directly on the connector or connected in circuit with terminal pins on the connector. An example of a flat circuit is a flat flexible circuit which includes a flat flexible dielectric substrate having one or more holes therein for receiving one or more terminal pins. A ductile conductive film or other circuit trace system is deposited on the substrate in an area at least about the hole or holes. The terminal pins are inserted into the holes in the substrate to establish electrical and mechanical connections between the pins and the flat flexible circuit. Typically, each hole is smaller in diameter than a respective pin. Alternatively, the pin may be punched through the flat flexible circuit to establish the electrical and mechanical connection therewith.
In order to assure good electrical and mechanical connections in these types of electronic devices or electrical connectors, solder or other adhesives often are used. For instance, in U.S. Pat. No. 4,970,624, dated Nov. 13, 1990 and assigned to the assignee of the present invention, uni-axial adhesive is deposited on the flat flexible circuit about the hole which is penetrated by the terminal pin. The adhesive includes a non-conductive base incorporating randomly spaced conductive particles. When the terminal pin is forced through the adhesive, a portion of the adhesive is carried with the terminal pin between the pin and the flat flexible circuit. The carried portion of the adhesive is compressed for establishing contact between the conductive particles and, thereby, conductivity between the terminal pin and the flat flexible circuit, leaving the adhesive other than that portion in a non-conductive state. Such adhesives often are called xe2x80x9cZ-axisxe2x80x9d adhesives. These adhesive were developed to replace soldering techniques which require specific temperature resistant components and substrates.
Conductive adhesives are used in other applications involving flat flexible circuits. For instance, in U.S. Pat. No. 5,456,616, dated Oct. 10, 1995 and assigned to the assignee of the present invention, the connector housing is fabricated of a die cast metallic material, such as of magnesium, aluminum or the like. The ductile film on the flat flexible circuit is fabricated of a different metallic material, such as copper or the like and, in fact, may be plated with still a different metallic material such as a tin/lead alloy. The conductive film on the flat flexible circuit acts as a ground plane against the rear face of the connector housing. The housing has a plurality of pins which project through holes in the flat flexible circuit. Using a xe2x80x9cZ-axisxe2x80x9d adhesive between the housing pins and the flat flexible circuit not only is expensive, as described above, but the conductive interface between the different metal components is limited to the areas of pressure. Consequently, that patent teaches the use of an omni-directional conductive adhesive deposited on the conductive film over the areas of the holes therein, the conductive adhesive expanding the conductive interface between the metal housing and the metal ground plane defined by the conductive film.
Although such uses of conductive adhesives, whether the adhesives are Z-axis adhesives or omni-directional adhesives, serve their intended purposes in certain applications, they are relatively expensive both in the cost of the adhesives as well as their methods of use. In addition, the use of either type of conductive adhesive is costly in terms of secondary operations and costs associated with the metal particles, not to mention the problem of clogging adhesive dispensers by the metallic particles.
Because of the problems associated with the use of conductive adhesives, a unique system was devised as disclosed in U.S. Pat. No. 5,384,435, dated Jan. 24, 1995 and assigned to the assignee of the present invention. That patent solves the problems with conductive adhesives by establishing an electrical connection directly between the terminal pin and the flat conductor on the flat flexible substrate by controlling various parameters between the pin and the substrate. Although this system has proven quite effective, there remains a continuing problem in electrical connectors or electronic devices wherein the pins are very closely spaced, i.e., in very high density connectors. In particular, if the interference between a pin and the substrate produces a stress in the substrate, the stress is magnified in high density applications and results in what is called a systematic stress that causes stress concentrations and can even result in substrate fractures. The present invention is directed to solving this myriad of problems in an extremely simple manner by producing an electrical connection between a contact pin and a flat circuit exclusively by compression which results in no stress being imparted to the substrate of the flat circuit. This unique system can be used in a wide variety of applications as will be seen herein.
An object, therefore, of the invention is to provide a new and improved electrical connector assembly of the character described.
In the exemplary embodiment of the invention, the electrical connector assembly includes a housing assembly having a bottom support structure with a top inside face and top support structure with a bottom inside face. A first flat circuit is mounted to the top inside face of the bottom support structure and includes a hole therethrough. A second flat circuit is mounted to the bottom inside face of the top support structure. At least one elongated conductive terminal extends into the bottom support structure and includes a laterally projecting wing portion for engaging an appropriate conductor on the first flat circuit. A head portion of the terminal engages an appropriate conductor on the second flat circuit. A spring portion of the terminal extends between the wing portion and the head portion to bias the wing portion and head portion in opposite directions into engagement with the respective conductors of the first and second flat circuits.
As disclosed herein, the terminal includes a mounting portion extending into a hole in the bottom support structure of the housing. A contact pin extends from the mounting portion beyond a bottom outside face of the bottom support structure for interconnection to a contact of an appropriate complementary connecting device. The spring portion of the terminal has a wave configuration. Preferably, a pair of the wing portions project laterally from opposite sides of the terminal. In one embodiment, the head portion of the terminal includes a rounded concave surface for engaging the conductor on the second flat circuit. In a second embodiment, the head portion includes a pair of bumps for engaging the conductor on the second flat circuit.
According to one aspect of the invention, the first flat circuit comprises a filter circuit, with at least one capacitor coupled to the conductor thereon. Preferably, the first flat circuit is a flexible circuit. In addition, a ferrite filter block is provided surrounding the terminal in the area of the spring portion thereof.
According to another aspect of the invention, the second flat circuit comprises a ceramic based power circuit. The top support structure comprises a metal heat sink.
Finally, the housing assembly includes a peripheral casting with an open top which is closed by the top support structure. The bottom support structure is formed by a dielectrical plastic member overmolded in an opening in the bottom of the peripheral casting.